A number of treatment and surgery procedures require a patient's eye to be stabilized or positioned prior to and/or during treatment. For example, refractive laser surgery involves ablating corneal tissue of the eye with an ultra-fast, ultra-short pulse duration laser beam. The ablation of selected corneal tissue can correct refractive errors in a patient's eye by permanently altering the structure of the cornea. To achieve ablation, refractive laser surgery requires a laser beam to be precisely focused to a very small focal spot within the cornea. As such, the patient's eye must be stabilized, and either the laser system must be properly and precisely aligned with the patient's eye, or the patient's eye must be properly and precisely aligned with the laser system.
In order to achieve proper alignment of the eye of the patient relative to the laser system, the system alignment settings and operating parameters must be well defined, steadfastly maintained, and frequently verified. Accurate and precise refractive surgery requires the corneal tissue be photoablated when the eye is substantially stabilized or stationary. Patient comfort and safety are also a consideration when holding the eye stationary and conducting laser surgery. Likewise, ocular radiotherapy treatment requires the eye to be stabilized and dynamically positioned during treatment. A major limitation of previous radiotherapy treatment systems is that eye position was not maintained and verified, with system shut-off occurring in the case where the eye travels out of position.
In order to achieve the goal of maximizing results while minimizing risks to the patient during such eye treatment, it is important to eliminate, or at least significantly reduce, as many system errors as possible. This includes the improper alignment of the patient's eye relative to the treatment system. Alignment errors may result from either a misconfiguration of the system, or from the patient's interaction with the system. Insofar as patient/system interaction is concerned, any voluntary or involuntary movement of the patient's eye during treatment can significantly alter the alignment of the eye relative to the treatment system. It is necessary, therefore, to hold the eye of the patient stationary during these procedures.
Several current laser surgery systems do not utilize direct contact between the eye and the laser system. However, when the eye is allowed to move independently of the system, maintaining an optical alignment of the eye with a laser or treatment system is problematic. For systems wherein a patient's eye is to be stabilized by placing the eye in direct contact with the system, stabilization can be established in two ways. The patient can be pre-positioned as desired, and the system then moved into contact with the eye. Such systems must be capable of being reconfigured to establish the necessary optical alignment. Alternatively, the system can be preconfigured with a desired alignment, and the patient then moved into contact with the system.
In addition to the operational issued discussed above, patient safety is also a concern. In particular, when the eye is in direct contact with the system, the magnitude of the interactive forces that are exerted on the eye are of concern. The variety of events that can cause these forces to exceed safety limits need to be avoided. Thus, there is a need for a treatment system which can physically manipulate the position of the eye, prevent undesired eye movement during treatment, provide needed safety precautions, and function as a positional reference between the surface of the eye, selected internal anatomy of the eye (e.g., the macula or optic nerve), and the system. The present system is designed to meet these needs.